It is a pastiche crossover which combines H. G. Wells's 1897 extraterrestrial invasion story with Sir Arthur Conan Doyle's Sherlock Holmes and Professor Challenger characters.

The book is composed of stories originally published in The Magazine of Fantasy & Science Fiction.

[1] The story consists of the adventures of Sherlock Holmes, Dr. Watson, and Professor Challenger in London during the Martian invasion as described in Wells's novel.

Conversely, in the Wellmans' book Holmes, Watson, and Challenger continually confront and outwit the Martians, undeterred by the invaders' technological superiority.

The story features a romantic relationship between Holmes and his landlady Mrs. Hudson, of which Watson is oblivious.